Islamist terrorists came within a hair's breadth of massacring one of Europe’s top football teams when they detonated three bombs close to a team bus, German authorities have revealed.

The three devices which exploded next to Borussia Dortmund’s coach were studded with metal shrapnel and pins, one of which pierced a window and embedded itself in a head rest.

The blast, which injured a player and a policeman, had a radius of more than 100 yards and federal prosecutors said it was lucky the toll was not more severe.

Detectives believe that only the strength of the team coach prevented the bombs causing mass casualties.

It has also been revealed that at least two men linked to Tuesday evening’s bombing were known Islamic State of Iraq and the Levant (Isil) sympathisers who had previously been on the radar of the German authorities.

The Borussia Dortmund team bus was hit by three explosions on Tuesday nightCredit: Kai Pfaffenbach/Reuters

Prosecutors are increasingly convinced an Islamist terror cell was behind the attack, which disturbingly showed far greater levels of sophistication and planning than the recent deadly lorry and car attacks in Stockholm and Westminster, which left nine people dead and dozens more injured.

The explosive devices were hidden in a hedge close next to a car park near the team’s hotel and may have been detonated by a call from a mobile phone used by someone close enough to track the coach’s movements.

The attack left Dortmund defender and Spanish international Marc Bartra requiring surgery on a broken bone in his wrist after he was hurt by flying glass.

On Wednesday afternoon he posted a picture of himself on Instagram and wrote on Twitter: "Hello! As you can see I am doing much better.

Thanks for all your messages! All my strength to my team mates, fans and to @BVB for tonight!"

A police officer escorting the coach was also left with hearing injuries by the blast from the explosion.

Following the attack police raided two apartments belonging to two men they described as “from the Islamist spectrum”. They arrested one man for questioning, a 25-year-old-Iraqi from Wuppertal. Another suspect was identified by local media as a 28-year-old German.

Head coach Thomas Tuchel, right, and players of Borussia Dortmund stand outside their team bus after it was damagedCredit: Martin Meissner/AP

Police were also seeking a car with foreign registered plates, which was seen near the scene shortly before the blasts took place.

The arrest came after three identical letters were found close to the scene of the team coach attack purporting to claim responsibility.

One was said to have been left "in the name of Allah, Most Gracious, Most Merciful" and referred chillingly to the Berlin Christmas market attack in December 2016, which killed 12 people and injured another 48.

It also accused Germany’s Chancellor Angela Merkel of “murdering Muslims” and demanded the ending of the country’s Tornado reconnaissance missions, part of an international coalition fighting Isil.

Lead prosecutor Frauke Koehle said: "Two suspects from the Islamist spectrum have become the focus of our investigation. Both of their apartments were searched, and one of the two has been detained."

A spokeswoman for Germany's federal prosecutor's office added: "We found several letters of responsibility. It appears that a possible Islamist motive is indeed possible. Among other things they demand the withdrawal of [German] tornado fighter jets from Syria and, I quote, ‘the closure of Ramstein airbase’.”

Drone operations against terrorist targets in the Middle East are controlled from the Ramstein base.

The three bombs were set off around 7.15pm local time in Dortmund’s Wittbräucker Str, as the squad was travelling to the Signal Iduna Park stadium for Tuesday's Champions League quarter-final first leg against Monaco.

The explosives were detonated minutes after the Dortmund team had bus pulled away from the squad's hotel and was heading towards the stadium, shattering the bus windows and scorching the side of the vehicle.

Dortmund's Swiss goalkeeper Roman Burki said: “The bus turned onto the main road, when there was a huge noise - a big explosion. After the bang, we all crouched down in the bus. We did not know if more would come."

Marcel Schmelzer, Borussia Dortmund's captain, said he did not at first suspect anything serious when the explosion happened, saying he asked himself: "Has someone thrown a stone at the bus again?"

A government spokesman said the full force of the German state was being brought to bear on tracking down those behind the plot.

Chancellor Merkel, speaking during an official visit yesterday, described the bombing as an “appalling act" and praised the "wonderful show of solidarity" of football fans across Germany and in Monaco following the attack.

"That is a clear signal against every kind of violence," she said. "We were all horrified yesterday when we heard about the attack on the Borussia Dortmund team's bus."

Ms Merkel’s official spokesman, Steffen Seibert, added: "It is a repugnant act. We are only relieved that it did not have more severe consequences.”

Heavy security was in place for the rescheduled Champion League football match in Dortmund on Wednesday night.

Extra forces were deployed around team hotels and their buses were taking ‘designated safe routes’ to the stadium. Dortmund's chief executive Hans-Joachim Watze vowed that his side "will not give in to terror".

He said: "We will play not only for ourselves today. We will play for everyone ... we want to show that terror and hate can never determine our actions.”

Monaco's vice president Vadim Vasilyev said: "Football must not be taken hostage."

Pictured: Heightened security ahead of tonight's match

These are the latest pictures reaching us from Dortmund, where security has been increased ahead of tonight's rescheduled Champions League quarter final tie between Borussia Dortmund and AS Monaco at the Signal Iduna Park.

Metal pin from bomb found embedded in headrest of bus seat

One of the metal pins from the bomb embedded itself in the headrest of one of the bus seats, and the bombs had an explosive effect that could reach more than 100 metres away, said Germany's federal public prosecutor.

Bomb was studded with metal pins, prosecutor reveals

The bomb was studded with metal pins, German's federal public prosecutor revealed, adding that the motive is still unclear, reports Melanie Hall.

A spokeswoman said the two male suspects, whose flats were searched by police and who are part of "the Islamist scene", were on the radar of authorities.

She confirmed that three identical letters with Islamist content claiming responsibility for the attack have been found, and said that theories over radical left-wing motives are currently being seen as unlikely.

Angela Merkel 'appalled' by Dortmund blasts

German Chancellor Angela Merkel is "appalled" by the Dortmund blasts, according to a government spokesman.

He said that Merkel had spoken to Borussia Dortmund boss Hans-Joachim Watzke and thanked him, the police and the fans for their calm behaviour.

The spokesman said investigators are doing "everything possible to track down the perpetrators", adding that the bombing differs from the Berlin truck attack "in that a letter of responsibility was found on site".

Angela Merkel 'named in letter claiming responsibility'

German Chancellor Angela Merkel is named in the 'Islamist' letter claiming responsibility for the attack, reports the DPA news agency. It is said to read:

"But apparently you don't care about your small, dirty subjects, Merkel. Your Tornados still fly over the caliphate's land in order to murder Muslims."

The one-page letter was typed with a computer rather than being handwritten.

Angela Merkel is reportedly named in the letterCredit: AFP

Investigators are checking the authenticity of the letter - intelligence agencies have emphasised that the background to the bomb attack is not yet known and that the letter could be a fake in order to lead investigators up the wrong track, reported newspaper Zeit.

Security tightened ahead of football matches

German police will bring in 80 more officers than previously planned to police tonight's Champions League match between Bayern Munich and Real Madrid that takes place in Munich, bringing the total number of officers to 450, reports Melanie Hall.

Police will also search the team's bus with sniffer dogs before the players board, and routes to the stadium will be checked. But the game will otherwise run as planned, with a police spokesman saying that they have not received any threats in Munich.

Meanwhile, there will also be increased security ahead of the rearranged Champions League quarter-final first leg between Borussia Dortmund and Monaco, which was postponed last night.

Investigators hunting for car with Belgian number plate

Bombs were 'remotely detonated in well-planned operation'

The perpetrator placed the bombs out of view of surveillance cameras at the team's hotel and then apparently remotely detonated them, suggesting a "very professional and well-planned operation," according to German newspaper Bild, reports Melanie Hall in Berlin.

Investigators said the impact would have been enough to kill people outside the bus, and that it is thanks to the bus' tough exterior that there were not worse injuries - something that the culprit might have underestimated.

Germany is 'on a death list of the Islamic State'

The first letter allegedly claimed that German warplanes are involved in murdering Muslims in the self-declared caliphate of Isil.

It also said sports stars and other prominent people "in Germany and other crusader nations" are on a "death list of the Islamic State".

The letter, published online, said the threat against high-profile public figures will last until German planes are withdrawn from the war zone, and the US air base at Ramstein, near the French border, is closed.

Football fans are not mentioned as targets and there is no signature, it was reported.

Damage to the Borussia Dortmund team busCredit: EPA/STR

Traces of the explosion are seen near the blastCredit: Maja Hitij/Getty

It also mentioned Germany's deployment of Tornado reconnaissance missions as part of an anti-IS international coalition, they reported.

The assault that wounded two, described by Dortmund city's police chief as a "targeted attack" against the team, shook German football ahead of crucial Champions League ties.

The Dortmund team had been leaving for the stadium to face Monaco when the blasts occurred.

Their match is now delayed until later Wednesday, when Bayern Munich are due to host Real Madrid for a separate Champions League game.

The games will take place under heightened security, with hotels of the players under guard and their buses driven to safe locations.

German authorities have until now held off from describing it as a terror attack, saying it is too early to determine a motive.

The Borussia Dortmund bus after the explosionsCredit: Maja Hitij/Getty

But the probe has now been taken over by federal prosecutors, whose remit includes terror investigations.

Germany has been on high alert since a series of jihadist attacks last year, including the Christmas market truck assault.

The explosives detonated minutes after the Dortmund team bus pulled away from the squad's hotel and headed for their quarter-final, first-leg tie against Monaco.

Dortmund's Marc Bartra was injured in the attackCredit: Alik Keplicz/AP

Spanish international Marc Bartra underwent surgery on a broken wrist after he was hit by flying glass. The injured policeman, who was on a motorcycle and had been escorting the team bus, suffered trauma from the noise of the blasts.

"We are assuming that they were a targeted attack against the Dortmund team," said the western German city's police chief Gregor Lange.